Prognostic significance of blood pressure variability in essential hypertension.

To assess the relation between BP variability, assessed using 24-hour noninvasive ambulatory BP monitoring (ABPM), and cardiovascular morbidity in essential hypertension, we followed up for up to 8.6 years (mean, 2.92) 1,372 patients with essential hypertension whose initial off-therapy diagnostic work-up included ABPM (one reading every 15 min for 24 hours). Patients, with standard deviation (SD) of daytime or nighttime systolic BP below or above the group mean (11.9 mmHg and 9.5 mmHg) were classified at low or high BP variability. Furthermore, 182 patients repeated ABPM and echo during follow-up, 2.7 years later. Target organ damage score was greater in the patients with high variability of daytime (p=0004) and nighttime (p=0.011) systolic BP than in those with low BP variability. In those who repeated ABPM and echocardiography, for every quartile of basal ambulatory BP, left ventricular mass at follow-up was greater (all p <0.05) in those with high basal BP variability than in those with low BP variability. During follow-up there were 106 major cardiovascular morbid events. The event rate was 1.99 and 3.26 events per 100 patient-yrs, respectively, in patients with low and high variability of daytime systolic BP, and 1.98 and 3.38 events per 100 patient-yrs respectively, in patients with low and high variability of nighttime systolic BP (log-rank test: both p<0.05). In a Cox multivariate analysis, variability scores of daytime and nighttime systolic BP failed to enter the model (age, diabetes, previous events and nighttime systolic BP showed a significant independent association with events). In conclusion, an increased BP variability, assessed with noninvasive ABPM, is associated with a higher incidence of cardiovascular morbid complications of hypertension, but its independent prognostic significance is obscured by age, diabetes, previous cardiovascular events and ambulatory BP. Noninvasive ABPM is not adequate to derive prognostic information from the assessment of BP variability in essential hypertension.